Eltrombopag, (Z)-3′-(2-(1-(3,4-dimethylphenyl)-3-methyl-5-oxo-1H-pyrazol-4(5H)-ylidene)hydrazinyl)-2′-hydroxybiphenyl-3-carboxylic acid is a compound having the following chemical structure:

It is a small-molecule, non-peptide thrombopoitin (TPO) receptor agonist that stimulates the proliferation and differentiation of megakaryocytes. Eltrombopag is marketed under the trade name Promacta® by GlaxoSmithKline and Ligand Pharmaceuticals as a bisethanolamine salt of the following chemical structure:
for the treatment of conditions leading to thrombocytopenia.
Eltrombopag is disclosed in U.S. Pat. Nos. 7,332,481 and 7,160,870; WO patent application 01/89457; and in EP patent No. 1294378.
Eltrombopag bisethanolamine salt is disclosed in US 2006/0178518 (corresponding to WO 03/098992).
Polymorphism, the occurrence of different crystal forms, is a property of some molecules and molecular complexes. A single molecule may give rise to a variety of polymorphs having distinct crystal structures and physical properties like melting point, thermal behaviours (e.g. measured by thermogravimetric analysis—“TGA”, or differential scanning calorimetry—“DSC”), x-ray diffraction pattern, infrared absorption fingerprint, and solid state NMR spectrum. One or more of these techniques may be used to distinguish different polymorphic forms of a compound.
Discovering new polymorphic forms and solvates of a pharmaceutical product can provide materials having desirable processing properties, such as ease of handling, ease of processing, storage stability, and ease of purification or as desirable intermediate crystal forms that facilitate conversion to other polymorphic forms. New polymorphic forms and solvates of a pharmaceutically-useful compound or salts thereof can also provide an opportunity to improve the performance characteristics of a pharmaceutical product. It enlarges the repertoire of materials that a formulation scientist has available for formulation optimization, for example by providing a product with different properties, e.g., better processing or handling characteristics, improved dissolution profile, or improved shelf-life. For at least these reasons, there is a need for additional polymorphs of Eltrombopag and Eltrombopag ethanolamine salt.